Many arthropods are capable of extracting information about color and polarization from incident photic stimuli. A mechanism has recently been proposed to account for the performance of retinular cells as analyzers of polarization; this performance is much better than would be predicted from the directly measured dichroic ratio of the photopigment- bearing structure (the rhabdomere). The mechanism involves the extracellular voltage changes caused by current flow around the tightly packed cells of single ommatidia. By utilizing a crustacean whose compound eye contains relatively large retinular cells, I will investigate this hypothesis, and I will also study other retinular cell-retinular cell interactions within ssngle ommatidia, such as tose which might arise via low-resistance junctions. The basic techniques involved are simultaneous intracellular recordng from pairs of cells, and marking of these cells by intracellular dye deposition. The experimental animal in the initial phases of this work will be the spiny lobster Panulirus, but other species will be surveyed in an attempt to find the one best suited for later phases of this investigaton.